UPDATE: You can do the steps below, and it will…. mostly work, but you’ll still run into broken things like, unable to enter text on the project config wizards or the bluetoot gatt configuration. The only _viable_ solution I’ve found really, is just to log out, and log in again choosing “Gnome on Xorg” and just not making wayland part of your daily headaches.

You still need the export GDK_BACKEND=x11 trick, and you still need the ./studio -Djxbrowser.chromium.dir=/home/$USER/.jxbrowser trick.

You also need to make sure you have git-lfs installed, or you will get fun errors like

/home/karlp/Downloads/SimplicityStudio_v5/developer/toolchains/gnu_arm/10.2_2020q4/bin/../lib/gcc/arm-none-eabi/10.2.1/../../../../arm-none-eabi/bin/ld:/home/karlp/SimplicityStudio/SDKs/gecko_sdk//protocol/bluetooth/lib/EFR32BG22/GCC/binapploader.o:1: syntax error

$ cat /home/karlp/SimplicityStudio/SDKs/gecko_sdk//protocol/bluetooth/lib/EFR32BG22/GCC/binapploader.o
version https://git-lfs.github.com/spec/v1
oid sha256:59b50942a2f0085fe2c87d0d038b13b8af279c742f0d3013b1d1ad6929070a3f
size 66088

Oops, that doesn’t look like a bootloader binary! This is actually mentioned on https://docs.silabs.com/simplicity-studio-5-users-guide/latest/ss-5-users-guide-overview/known-issues as issue 76584, but you wouldn’t find that til later. The tips are to reinstall, but you can also

cd ~/SimplicityStudio/SDKs/gecko_sdk && git lfs fetch && git lfs pull && echo "whew, that took aaaages"

You can _probably_ do tricks with git lfs to just pull the single files you need, and avoid pulling the 800meg or something at 1meg/sec that it took, but this got me a building and functional simplicity studio! wheee…..